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- Deposition process (3) (entfernen)
Low- and atmospheric-pressure plasma co-polymerisations of binary gas mixtures of C2H4 and NH3 or N2, respectively, were investigated for depositing N-rich plasma polymer coatings for biomedical applications. Deposition kinetics and relevant surface characteristics of resulting plasma polymerised ethylene enriched with nitrogen, PPE:N, coatings were investigated as a function of the gas mixture ratio, X = NH3(N2)/C2H4. Physico-chemical properties of the coatings were determined using a combination of complementary surface-sensitive techniques: for example, total nitrogen concentrations, [N], up to 40 at.% were measured by X-ray Photoelectron Spectroscopy, XPS, while those of primary amines, [NH2], were determined by performing chemical derivatisation followed by XPS analyses. PPE:N films were further characterised by UVVIS Ellipsometry, Near Edge X-ray Absorption Fine Structure Spectroscopy, IR Spectroscopy and by Contact Angle Goniometry measurements. The stability of the coatings was tested, both in terms of water solubility and of ageing in ambient atmosphere. For the latter, selected samples were stored in the laboratory for different durations, in order to assess possible changes in their chemical structures.
Selected FTIR, XPS and NEXAFS spectroscopy results obtained with films deposited with different plasma polymerization processes and different monomers (styrene, acetylene, ethylene and butadiene) are presented. In detail FTIR spectra, XPS surveys, XPS valence bands and core level signals including shake-up features as well as carbon K-edge absorption spectra are qualitatively and, in some cases, semi-quantitatively considered. Information on the film formation, the chemistry of the films and the film stability against air exposure are derived from spectroscopic features. With styrene chemically rather well defined plasma polymer layers can be formed with rather high deposition rates applying a pulse plasma process. Using ethylene, acetylene or butadiene as a monomer in the plasma deposition process the deposition rates are smaller. Using these monomers plasma polymer films can be obtained with a primary chemical structure which is similar to each other but more or less different from those of the respective conventional polymers. The main difference between these samples is their individual concentration of unsaturated carbon species. Finally, a technologically relevant example, i.e. a plasma deposited polymer barrier layer deposited on the inner wall of a poly(ethylene) vessel is briefly considered.
The Spray Ion Layer Gas Reaction (Spray-ILGAR) technique is a new variation on the ILGAR technique used to prepare chalcogenide thin films. High quality indium sulfide thin films were produced by Spray-ILGAR with an indirect bandgap of 2.2 eV and a high suitability for use as buffer layers in chalcopyrite solar cells. The process involves the cyclical spray deposition of an indium containing precursor layer followed by its conversion to sulfide using hydrogen sulfide gas. Analysis of the deposition reveals that the indium chloride based precursor is transported via the vapour phase from the spray droplets to the substrate surface.